Inhibiting process and product



POSlTlONS,

Patented Niay 29 1934 UNITED STATES LAClHllHux PATENT OFFICE 1,961,097INHIBITING PROCESS AND PRODUCT Orin D. Cunningham,

to Peter C. Reilly,

No Drawing.

15 Claims.

This invention relates to the prevention or retardation of chemicalaction of acid or salt solutions on metals in certain chemical andelectrochemical processes, and the consequent pre- .vention orretardation of the evolution of hydrogen at the surface of metalsimmersed in such acid or salt solutions; by certain products hereindescribed as inhibitors.

The object of the present invention is to produce a highly efficientinhibitor.

My invention is especially useful in what is commonly referred to as thepickling process, wherein metals, such for example as iron or steel, aresubjected to the action of acid solutions for removing the oxide scalefrom the surface thereof; in which process the presence of very smallquantities of the inhibitor reagents of the present invention dissolvedin the acid pickling solution results in a very marked retardation ofthe corrosive action on the metal and the consequent evolution ofhydrogen gas, without materially interferring with the action of theacid in removing the scale, rust, or oxide film from the surfacethereof. Thereby not only is a material saving in acid and metaleffected, but certain objectionable features incident to the picklingoperation without an inhibiting reagent are overcome. For example, theevils known as acid brittleness, blisters, black deposits, andoverpickling are greatly mitigated; and the highly objectionable sprayof acid (acid fumes) the atmosphere by the excessive hydrogen gasevolution formed in the absence of inhibiting agent is substantiallyeliminated.

In its broader aspects, however, my invention contemplates the use ofthe inhibitor reagents of the present invention in acid or saltsolutions of any chemical or electrochemical process which under normalconditions will evolve hydrogen at the surface of the metal in contacttherewith; and also in the storage of certain corrosive acid or saltsolutions. In the electrodepositions of metals, for example, it may findapplication in retarding the sometimes troublesome evolution at thecathode without in any way interfering with normal operation of theprocess. It may further be applied in acid cleaning solutions, to retardcorrosive action of the acid on the metal, such as, for example,automobile radiator cleaning solutions. I have discovered that certainof stituted dithiobiuret compounds posses excellent inhibiting action onthe evolution of hydrogen, especially those dithiobiuret compounds whichare obtained by the reaction of perisosulfocyanic acid with a substancein the class comprising aniline and its homologs.

By aniline and its homologs I include the aromatic primary basesaniline, the toluidines, and the xylidines; and theiraliphatic-alkyl-subthe sub- Indianapolis, I nd., assignm- Indianapolis,Ind.

Application May 9, 1932, erial No. 610,316

stituted secondary bases methylaniline, ethylaniline, etc.,methyltoluidine, ethyltoluidine, etc., methyl xylidine, ethyl xylidine,etc.; as well as the mono-substituted halides of these aminocomchloroanilines,

Any dethese compounds may also be used; and they may be pure, partiallyrefined, or crude materials.

The monosubstituted dithiobiuret compounds herein disclosed may berepresented by the following formula:

In these formulas, R1 represents a hydrocarbon radical or a hydrocarbonradical containing a halogen, and R2 represents a hydrocarbon radical orhydrogen.

The reaction according to the preferred method of obtaining this type ofcompound is illustrated by the following equation, which depicts thereaction of aniline with perisosulfocyanic acid to form phenyldithiobiuret.

cyanic acid (i-NH:

tion of the inhibitor reagents of the present invention.

Example 1 To 100 parts by weight of aniline (or of toluidine orxylidine, or of aliphatic-ethyl-substituted aniline, toluidine, orxylidine) are added 100 parts of perisosulfocyanic acid and the reactionmixture heated to 120 C., or thereabout, for 5-10 hours with agitation.These proportions provide an excess of aniline, which I deem itdesirable to have as a reaction medium although it is not necessary. Thereaction product is a solid material.

Example 2 This example is the same as Example 1, save that the reactionis carried out at 100 C. for about ten hours in the presence of 100parts by volume of 22 B. hydrochloric acid as a reaction medium. Thereaction product is a semisolid material.

Instead of hydrochloric acid as a reaction medium other mineral acidsmay be used, such as, for example, sulfuric acid. The reaction mediummay be employed in any desired proportion or concentration. The reactionmay also be carried out in organic reaction mediums, such as benzene ortoluene, as well as the excess of aniline provided in Example 1, and anyreaction medium may be used which permits the reaction to proceed.

In a similar manner any of the above-mentioned homolog compounds ofaniline may be reacted with perisosulfocyanic acid to produce thesubstituted dithiobiuret type of inhibitor reagent herein disclosed, ora mixture of aniline and its homolog compounds may be employed.

My invention is not limited to any specific proportion of aniline andits homolog compounds, nor is there any limitation on the proportion ofperisosulfocyanic acid in the reaction. I prefer to have an excess ofthe aniline or its homolog compounds, as already stated, but that is notessential.

Furthermore it is possible in some cases to vary the concentrations ofthe reacting materials, and of the reaction medium, to obtain eitherliquid or solid (or semi-solid) reaction products as desired, any one ofwhich is effective as an inhibiting reagent.

In general it may be said that in the use of the inhibitor reagents ofthe present invention one percent or less added to the acid or saltsolution is sufiicient to obtain optimum effect, although larger amountsmay be used if desired.

As a specific example of the inhibiting action of the inhibitor reagentscoming within the scope of this invention, when applied to pickling ofsteel, 0.004 of 1% by weight of the solid reaction product ofperisosulfocyanic acid with aniline, produced according to Example 1,when added to a pickling solution of 82 (3., containing 6% by weight ofsulfuric acid, there was obtained a metal-loss of 2.7 milligrams persquare inch for a forty-minute pickling period after de-scaling wascomplete, as compared to 122.0 milligrams per square inch for the sametest without any inhibitor present; and a proportionately reducedevolution of hydrogen.

Under the above pickling conditions the corrosive action on the iron andconsequent evolution of hydrogen was substantially prevented without anymaterial interference with the desired function of the picklingoperation-namely, the removal of the scale or oxide film from the metalsurface.

By regulating the concentration of the inhibitor it is possible toobtain practically any desired degree of inhibiting action.

The above example of the use of my inhibitors is illustrative only, andnot at all to limit the scope of the invention. For instance, othermetals and alloys may be similarly treated, such as copper, nickel,brass, stainless steel, etc. Different pickling acids, or acidconcentrations, may be employed, or the period of treatment and thetemperature employed may be varied to suit the manufacturing needs.

Mixtures of my various inhibitor reagents with other known inhibitorscan be used to advantage to obtain improved results.

These inhibitors can be used in the presence of the foam-producingagents commonly employed in the pickling operation, without detriment tothe effect of either.

I claim as my invention:

1. The process of inhibiting the solution of a metal the surface ofwhich is in contact with or immersed in an acid or salt solution, and soinhibiting the consequent evolution of' hydrogen, consisting indissolving in said acid or salt solution a small amount of a substituteddithiobiuret compound having the following formula:

CSNH:

in which R1 represents a hydrocarbon radical or a hydrocarbon radicalcontaining a halogen, and R2 represents hydrogen or a hydrocarbonradical.

2. The process of inhibiting the solution of a metal the surface ofwhich is in contact with or immersed in an acid or salt solution, and soinhibiting the consequent evolution of hydrogen, consisting indissolving in said acid or salt solution a small amount of phenyldithiobiuret.

3. The process of inhibiting the solution of a metal the surface ofwhich is in contact with or immersed in an acid or salt solution, and soinhibiting the consequent evolution of hydrogen, consisting indissolving in said acid or salt solution a small amount of a product ofthe reaction of perisosulfocyanic acid with a substance from the classconsisting of aniline and its homologs.

4. The process of inhibiting the solution of a metal the surface ofwhich is in contact with or immersed in an acid or salt solution, and soinhibiting the consequent evolution of hydrogen, consisting indissolving in said acid or salt solution a small amount of a product ofthe reactionof perisosulfocyanic acid with aniline.

5. The process of inhibiting the solution of a metal the surface ofwhich is in contact with or immersed in an acid or salt solution, and soinhibiting the consequent evolution of hydrogen, consisting indissolving in said acid or salt solution a small amount of a product ofthe reaction of perisosulfocyanic acid with an excess of a substancefrom the class consisting of aniline and its homologs.

6. The process of inhibiting the solution of a metal the surface ofwhich is in contact with or immersed in an acid or salt solution, and soinhibiting the consequent evolution of hydrogen, consisting indissolving in said acid or salt solution a small amount of a product ofthe reaction of perisosulfocyanic acid with an excess of aniline.

'1. A liquid bath for chemical and electro-chemical purposes, comprisingan acid or salt solution 252. COMPOSlTlONS,

' containing a small amount of a substituted dithiobiuret compoundhaving the following formula:

CSNH:

in which R1 represents a hydrocarbon radical or a hydrocarbon radicalcontaining a halogen, and R2 represents hydrogen or a hydrocarbonradical.

8. A liquid bath for chemical and electro-chemical purposes, comprisingan acid or salt solution containing a small amount of phenyldithiobiuret.

9. A liquid bath for chemical and electro-chemical purposes, comprisingan acid or salt solution containing a small amount of a product of thereaction of perisosulfocyanic acid with a substance from the classconsisting of aniline and its homologs.

10. A liquid bath for chemical and electrochemical purposes, comprisingan acid or salt solution containing a small amount of a product of thereaction of perisosulfocyanic acid with aniline.

11. A pickling bath, comprising sulphuric acid containing a substituteddithiobiuret compound having the following formula:

in which R1 represents a hydrocarbon radical or a hydrocarbon radicalcontaining a halogen. and

R: represents hydrogen or a hydrocarbon radical.

12. A new inhibitor for use in the cleaning of metal surfaces with acidor salt solutions, consisting of a substituted dithiobiuret compoundhaving the following formula:

in which R1 represents a hydrocarbon radical or a hydrocarbon radicalcontaining a halogen, and R2 represents hydrogen or a hydrocarbonradical.

13. A new inhibitor for use in the cleaning of metal surfaces with acidor salt solutions, consisting of phenyl dithiobiuret.

14. A new inhibitor for use in the cleaning of metal surfaces with acidor salt solutions, consisting of a product of the reaction ofperisosulfocyanic acid with a substance from the class consisting ofaniline and its homologs.

15. A new inhibitor for use in the cleaning of metal surfaces with acidor salt solutions, consisting of a product of the reaction ofperisosuliocyanic acid with aniline.

ORIN D. CUNNINGHAM.

